Indicator definition

Definition: The indicator shows trend in in annual average global surface temperature. The global average temperature change in the charts have been compared to be pre-industrial times.

Model used: IMAGE

Ownership: Netherlands Environmental Assessment Agency (MNP)

Temporal coverage: 2000 - 2100

Geographical coverage: global

Units

oC (degrees Celcius)

Key policy question: Will the increase in global average temperature stay within the EU policy target of not more than 2 degrees Celsius (C) above pre-industrial levels, and will the rate of increase in global average temperature stay within the proposed target of not more than 0.2 degree C per decade?

Key messages

The annual average temperature for Europe is projected to increase by 1.0-5.5 °C (comparing 2080-2100 with the 1961-1990 average). The warming is projected to be greatest over eastern Europe, Scandinavia and the Arctic in winter (December to February), and over south-western and Mediterranean Europe in summer (June to August) (Giorgi et al., 2004; IPCC, 2007a).

Modelled change in mean temperature over Europe between 1980-1999 and 2080-2099

Key assessment

The global and European average temperature is projected to continue to increase. Globally, the projected increase in this century is between 1.8 and 4.0 °C (best estimate), and is considered likely (66 % probability) to be between 1.1 and 6.4 °C for the six IPCC SRES scenarios and multiple climate models (see Chapter 4 of EEA Report No 4/2008), comparing the 2080-2100 average with the 1980-1999 average. These scenarios assume that no additional policies to limit greenhouse gas emissions are implemented (IPCC, 2007a). The range results from the uncertainties in future socio-economic development and in climate models. The EU "sustainable" target of limiting global average warming to not more than 2.0 °C above pre-industrial level is projected to be exceeded between 2040 and 2060, for the all six IPCC scenarios.

The annual average temperature for Europe is projected to increase by 1.0-5.5 °C (comparing 2080-2100 with the 1961-1990 average). This range takes into account the uncertainties in future socio-economic development by including two of the IPCC-SRES scenarios (the high emissions A2 and the medium emissions A1b), and the uncertainties in the climate models (Christensen et al., 2007) (Map 5.2). The warming is projected to be greatest over eastern Europe, Scandinavia and the Arctic in winter (December to February), and over south-western and Mediterranean Europe in summer (June to August) (Giorgi et al., 2004; IPCC, 2007a). The temperature rise in parts of France and the Iberian Peninsula may exceed 6 °C, while the Arctic could become on average 6 °C and possibly 8 °C warmer than the 1961-1990 average (IPCC, 2007a, 2007b; ACIA, 2004).

Justification for indicator selection

Temperature is directly linked to climate change and is a state variable that changes in response to the pressures of global warming. Surface air temperature gives one of the clearest signals of climate change, especially in recent decades. It has been measured for many decades or even centuries. There is mounting evidence that anthropogenic emissions of greenhouse gases are (mostly) responsible for the recently observed rapid increases in average temperature. Natural factors like volcanoes and solar activity could to a large extent explain the temperature variability up to middle of the 20th century, but can explain only a small part of the recent warming.

Absolute temperature changes and the rate of change are both important determinants of the possible effects of climate change. These include rising sea levels, floods and droughts, changes in biota and food productivity and increase of infectious diseases. Trends and projections of the annual average temperature are easy to understand and can be related to the targets. However, they do not show spatial and seasonal differences. Next to the global average target, is the rate and spatial distribution of temperature change is important, for example for determining the possibility of natural ecosystems adapting to climate change. Temperature in Europe exhibits large differences from the west (maritime) to east (continental), and from south (Mediterranean) to North (Arctic) and regional differences; winter/summer temperatures and cold/hot days illustrate temperature variations within a year.

Scientific references:

No rationale references
available

Policy context and targets

Context description

Over a decade ago, most countries joined an international treaty -- the United Nations Framework Convention on Climate Change (UNFCCC) - to begin to consider what can be done to reduce global warming and to cope with whatever temperature increases are inevitable. Recently, a number of nations have approved an addition to the treaty: the Kyoto Protocol. The Kyoto Protocol, an international and legally binding agreement to reduce greenhouse gases emissions world wide, entered into force on February 16th 2005. The 1997 Kyoto Protocol shares the Convention's objective, principles and institutions, but significantly strengthens the Convention by committing Annex I Parties to individual, legally-binding targets to limit or reduce their greenhouse gas emissions.

Kazakhstan has signed but not ratified the protocol. It expects to enter into quantitative GHG reduction obligations for the period of 2008-2012 and expects to become a full participant of the three Kyoto mechanisms. (Strategy of the Republic of Kazakhstan on Climate Change). Bosnia and Herzegovina, Serbia and Montenegro, Tajikistan and Turkey have no commitments as they did not sign or ratify the Protocol.

At the EU level the aims for reduction of the impact on Climate is expressed in the EC 6th Environmental Action Programme, EC 2006 Green paper on energy and a number of Council Decisions (see policy targets).

EECCA Environmental Strategy emphasizes importance of measure in energy and transport sectors in order to reduce Climate Change.

Targets

Global level

The UNFCC Convention and the Kyoto Protocol do not put individual targets for global temperature but they provide general policy context.

EU level

To avoid serious climate change impacts, the European Council proposed in its sixth environmental action programme (6EAP, 2002), reaffirmed by the Environment Council and the European Council of 22-23 March 2005 (Presidency Conclusions, section IV (46)), that the global average temperature increase should be limited to not more than 2 degrees C above pre-industrial levels (about 1.3 degrees C above current global mean temperature). In addition, some studies have proposed a 'sustainable' target of limiting the rate of anthropogenic warming to 0.1 to 0.2 degrees C per decade (Leemans and Hootsman, 1998, WBGU, 2003).

The targets for both absolute temperature change (i.e. 2 degrees C) and rate of change (i.e. 0.1-0.2 degrees C per decade) were initially derived from the migration rates of selected plant species and the occurrence of past natural temperature changes. Although studies have indicated that such changes might still result in impacts in various vulnerable regions, both targets have been confirmed as (a) suitable (target) from both a scientific and a political perspective (e.g. Leemans and Hootsmans, 1998, WBGU, 2003).

Related policy documents

Council Decision (2002/358/EC) of 25 April 2002 concerning the approval, on behalf of the European Community, of the Kyoto Protocol to the United Nations Framework Convention on Climate Change and the joint fulfilment of commitments thereunder.

Decision No 280/2004/EC of the European Parliament and of the Council of 11 February 2004 concerning a mechanism for monitoring Community greenhouse gas emissions and for implementing the Kyoto Protocol

Methodology

Methodology for indicator calculation

The global surface temperature change since pre-industrial times (1765) is calculated in the upwelling-diffusion climate model (UDCM) which is included as a one of the main components into the IMAGE 2.2. SRES Scenarios Model. In the UDCM four boxes are distinguished: land in northern and southern Hemisphere and ocean in northern and southern hemisphere. The temperature change of each of these boxes is based on the heat-absorbing capacity of the 40 oceanic layers. This heat-absorbing capacity is modelled for each oceanic box with an upwelling-diffusion energy-balance model. Therefore, each box has a different profile of temperature change. The global surface temperature is calculated as a weighted mean of the four boxes. The weights depend on the area within each box.

This indicator shows the most striking differences between low climate sensitivity runs (B1_low and A1F_low), high climate sensitivity runs (B1_high and A1F_high) and the main scenario runs (with medium climate sensitivity) (see uncertainties).

Overveiw of the UDCM model

The Upwelling-Diffusion Climate Model (UDCM) of IMAGE 2.2 represents the core-model of the Atmospheric Ocean System (AOS). UDCM converts the concentrations of the different greenhouse gases and SO2 emissions into radiative forcings and successively into temperature changes of the global-mean surface and the ocean. UDCM is based on the MAGICC-model of Climate Research Unit (CRU) (Hulme et al., 2000). The MAGICC model is the most widely used simple climate model within the IPCC (2001). More details on MAGICC can be found in Raper et al. (1996) and Hulme et al. (2000). The implementation of MAGICC in IMAGE 2.2 and the calculation of the radiative forcings is described by Eickhout et al. (2001).

Methodology for gap filling

Historical data for the 1765-1995 period are used to initialise the carbon cycle and climate system. IMAGE 2.2 simulations cover the 1970-2100 period. Data for 1970-1995 are used to calibrate EIS and TES. Simulations up to the year 2100 are made on the basis of scenario assumptions on, for example, demography, food and energy consumption and technology and trade. Models are used for projections and gap fillings.

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

Many unknowns and uncertainties in the climate system are not reflected in the IMAGE scenarios. Some of the major uncertainties in the causal chain are the climate sensitivity and regional climate-change patterns. The direct effects of a changed climate are changes in carbon uptake by the biosphere and oceans and in the distribution and productivity of crops, as well as shifts in ecosystems. Indirectly, many other processes are influenced, which can lead to the concentrations of greenhouse gases in the atmosphere being built up differently and to different land-use patterns. IMAGE simulates the consequences of these changes in an integrated fashion, accounting for interactions and feedbacks. The outcome is thus not necessarily a linear function of climate sensitivity.

These climate uncertainties were addressed by providing additional simulations to illustrate the uncertainty in the climate sensitivity and in the regional climate-change patterns.

Climate sensitivity

Climate sensitivity refers to long-term (equilibrium) change in global mean surface temperature following a doubling of the atmospheric concentration in CO2 equivalents. According to IPCC, this climate sensitivity is between 1.5oC and 4.5oC. In earlier versions of IMAGE, the climate sensitivity generated by the climate model was 2.4oC. Due to the rigid structure of these earlier versions, we were unable to change this and assess the consequences of such a change.

In IMAGE 2.2 a simpler climate model MAGICC (see Upwelling-Diffusion Climate Model) is incorporated, allowing to define the climate sensitivity. The default value for IMAGE runs is 2.5, which is the median value of the IPCC range (median differs from mean because the range is logarithmic).

To test the uncertainty related to the climate sensitivity, runs with respectively a low (1.5oC) and high (4.5oC) climate sensitivity were created. A pattern-scaling procedure is used to obtain regional and seasonal climate-change patterns using the calculated increase in global mean temperature.

Runs with changed climate sensitivity are provided for the A1F (A1F low, A1F high) and B1 (B1 low, B1 high) scenarios on the main disc (IMAGE team 2001a). These scenarios span the full range of the SRES emission scenarios and therefore adequately illustrate the uncertainty of different climate sensitivities.

Regional climate-change patterns

Climate-change patterns are not simulated explicitly in IMAGE. The global mean temperature increase, as calculated by IMAGE, is linked with the climate patterns generated by a general circulation model (GCM) for the atmosphere and oceans. This linking takes place using the standardized IPCC pattern-scaling approach (Carter et al., 1994) and additional pattern-scaling for the climate response to sulphate aerosols forcing (Schlesinger et al., 2000; see Geographical Pattern Scaling, GPS). GCMs are currently the best tools available for simulating the physical processes that determine global climate dynamics and regional climate patterns.

GCMs simulate climate over a continuous global grid with a spatial resolution of a few hundred kilometres and a temporal resolution of less than an hour.

Most GCMs agree on the global patterns of climate change:

temperature increases above land are faster than above the oceans

high latitudes warm up more sharply than low latitudes

winter warms up more sharply than summers

total precipitation increases with increasing temperature

maritime regions generally get wetter

continental regions could get dryer.

Regionally, however, there are large differences between the different GCMs, especially in precipitation-change patterns.

IMAGE 2.2 runs with five different climate-change patterns are provided on the supplementary disc (IMAGE team 2001b, RIVM CD-ROM publication 481508019) for the A1F, B1 and A2 scenarios. The aim of this material is to illustrate the uncertainties in SRES climate-change scenarios resulting from these differences in GCMs. The first two scenarios span the full range of the SRES emission scenarios, the latter being based on a highly different narrative with different demographic and socio-economic assumptions. The three scenarios therefore adequately illustrate the uncertainty of different climate patterns. Differences in the runs for each scenario indicate some of the uncertainty caused by regional variation in climate-change patterns (not the global mean).

The scenarios for five different GCM runs from the IPCC data centre were implemented, which comprised:

ECHAM4 of the Deutsches Klimarechenzentrum DKRZ in Germany

CGCM1 of the Canadian Centre for Climate Modelling and Analysis in Canada

GFDL-LR15-a of the Geophysical Fluid Dynamics Laboratory in the USA

HADCM2 of the Hadley Centre for Climate Prediction and Research in the UK

CSIRO-MK2 of Commonwealth Scientific and Industrial Research Organisation in Australia

Data sets uncertainty

The input data to the UDCM model is atmospheric concentrations of greenhouse gases and emissions of SO2, which by itself is calculated on the basis of the other IMAGE 2.2. Models and bare all uncertainties related to those models (see more in methodology uncertainly).

Rationale uncertainty

The observed increase in average air temperature, particularly during the recent decades, is one of the clearest signals of global climate change

The indicator shows trends in temperature data over time. Temperature is directly linked to the question of climate change and is a state variable that changes in response to the pressures of global warming.

There is growing evidence that anthropogenic emissions of greenhouse gases are (mostly) responsible for the recently observed fast increases in average temperature. Natural factors like volcanoes and sun activity could explain to a large extent the temperature variability up to mid of the 20th century, but they can explain only a small part of the recent warming.

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